Displacing a substance

ABSTRACT

According to some examples a substance displacement apparatus may comprise a gas ejection aperture and a deflector arm. The gas ejection aperture may be to direct gas towards a roller having a surface on which a substance is disposed. The deflector arm may be moveable between a first position in which gas is directed away from a target area on the surface of the roller, and a second position in which gas is directed towards the target area on the surface of the roller, thereby to displace at least some of the substance from the surface of the roller within the target area. A method and a print apparatus are also disclosed.

PRIORITY INFORMATION

This application is a continuation of U.S. National Stage applicationSer. No. 16/606,213 filed on Oct. 17, 2019, which claims priority toInternational Application No. PCT/US2018/012729 filed on Jan. 8, 2018.The contents of which are incorporated herein by reference in itsentirety.

BACKGROUND

In a printing press, a substance, such as print agent, a coating or avarnish may be applied to a plate mounted on a roller for subsequenttransfer onto a printable substrate. In some examples, it may beintended that the substance is not to be transferred onto the substratefrom a particular portion of the plate, for example to cause a portionof the substrate corresponding to that particular portion of the plateto remain uncoated or unprinted.

If the position of the portion to remain uncoated or unprinted changes,or the shape of the portion changes, then the plate on the roller may bereplaced with a different plate having the new intended printingarrangement. However, producing a new plate and replacing the plate onthe roller may be costly and time consuming.

BRIEF DESCRIPTION OF DRAWINGS

Examples will now be described, by way of non-limiting example, withreference to the accompanying drawings, in which:

FIG. 1 is a simplified schematic of an example of a printing system;

FIG. 2 is a simplified schematic of an example of a substancedisplacement apparatus;

FIG. 3 is a simplified schematic of a further example of a substancedisplacement apparatus;

FIG. 4 is a simplified schematic of a further example of a substancedisplacement apparatus;

FIG. 5 is a simplified schematic of an example of a portion of asubstance displacement apparatus in a first configuration:

FIG. 6 is a simplified schematic of an example of the portion of thesubstance displacement apparatus in a second configuration;

FIG. 7 is a simplified schematic of a further example of a substancedisplacement apparatus;

FIG. 8 is a flowchart of an example of a method for displacing asubstance;

FIG. 9 is a flowchart of a further example of a method for displacing asubstance;

FIG. 10 is a simplified schematic of an example of a print apparatus;and

FIG. 11 is a simplified schematic of a further example of a printapparatus.

DETAILED DESCRIPTION

Examples in the present disclosure describe apparatus, systems andmethods for selectively displacing a substance from a surface, such as asurface of a roller in a printing apparatus, for example.

FIG. 1 shows, schematically, an example of a printing system 100 inwhich it may be intended to displace substance from a surface of aroller. The printing system 100 may include a first roller 102, such asan anilox roller. An anilox roller may, in some examples, comprise ametallic core surrounded by a ceramic coating. The surface of theceramic coating may include thousands or millions of indentations,referred to as cells, having a defined capacity. A substance, such asprint agent, primer, ink, varnish or the like, may be deposited on theroller, for example from a substance container or source 104. Excesssubstance may be removed (e.g. scraped) from the surface of the rollerusing a doctor blade 106 and/or a substance displacement apparatus 200(discussed in greater detail below). A defined amount of the substancemay be left in the cells. The first roller 102 may then be rotated incontact with a printable substrate 108, which may be in the form ofindividual sheets or a web (as shown in the example of FIG. 1). In someexamples, the system 100 may further include a second roller 110, suchas a nip roller, which rotates in an opposite direction to the firstroller 102, and which serves to urge the printable substrate 108 towardsthe first roller while print agent is transferred from the first rolleronto the printable substrate. In some examples, the second roller 110may be omitted or replaced with some other component, such as a supportto support the printable substrate 108.

During some printing jobs, it may be intended to prevent any substancefrom being deposited onto a particular area or region of the printablesubstrate 108, or at least restrict the amount of substance depositedonto the particular area or region. For example, when printing a web ornet to be formed into a packaging container, such as a carton for foodor drink, it may be intended that some parts of the carton (e.g.attachment tabs) are to be glued and stuck to other parts of thepackaging web and, therefore, should not receive any print agent. Inother examples, such a packaging web may be coated in a waterproofcoating or varnish. Again, it may be intended that some portions of thepackaging, such as the tabs, are not to be coated by the varnish orcoating. In another example, it may be intended that a region on thepackaging web is to remain unprinted (referred to as a knockout), sothat a “use by” or “best before” date may be printed subsequently inthat region. In such examples, in order to prevent substance (e.g. inkor varnish) from being deposited onto the printable substrate 108, theprint agent may be removed or displaced from those cells on the aniloxroller 102 which correspond to the region to remain unprinted oruncoated. As discussed in detail below, the substance displacementapparatus 200 serves to selectively remove or displace a substance froma region or regions on the roller 102.

While the example system 100 discussed above includes an anilox roller102, in other examples, rollers of other types may be included in thesystem instead of, or in addition to, the anilox roller. For example,the substance displacement apparatus 200 may remove print agent from thesurface of a roller other than an anilox roller, which is intended to beused to transfer print agent (or some other substance) onto a printablesubstrate 108.

In general, the substance displacement apparatus 200 uses a flow of gasto displace a substance, such as print agent or varnish or the like,from a surface of a roller. Various gases or combinations of gases maybe used, such as compressed air, carbon dioxide, nitrogen, or the like.In some examples, high humidity compressed air may be used as this mayreduce the drying effect of water-based substances. In order to achieveaccurate control over the flow of the gas and, therefore, over theregions on the roller at which the gas is directed, the substancedisplacement apparatus 200 uses a mechanism for deflecting the flow ofgas into an intended direction.

FIG. 2 is a simplified schematic of an example of the substancedisplacement apparatus 200. The substance displacement apparatus 200comprises a gas outlet, or gas ejection aperture 202, to direct gastowards a roller having a surface on which a substance is disposed; anda deflector arm moveable between a first position in which gas isdirected away from a target area on the surface of the roller, and asecond position in which gas is directed towards the target area on thesurface of the roller, thereby to displace at least some of thesubstance from the surface of the roller within the target area. In someexamples, the roller may comprise a roller such as the anilox roller102. Thus, in general, when it is intended to direct gas towards thesurface of the roller so as to displace the substance from the rollersurface in a particular area, the deflector arm may be positioned suchthat the flow of gas is towards the particular area on the rollersurface. However, when it is not intended for the flow of gas to bedirected towards the particular area on the roller (e.g. when it isintended for the substance to remain on the surface of the roller inthat particular area), then the deflector arm may be positioned suchthat the gas flow is not towards the particular area on the rollersurface, or is prevented from reaching the particular area of the rollersurface.

FIG. 3 shows, schematically, a cross-section through one particularexample of the substance displacement apparatus 200. In the exampleshown in FIG. 3, the gas ejection aperture 202 is located between afirst housing portion 302 and a second housing portion 304. Thedeflector arm 204 extends into the gas ejection aperture 202 between thefirst and second housing portions 302, 304. In some examples, thedeflector arm 204 may at least partially through the gas ejectionaperture 202 between the first and second housing portions 302, 304.

In some examples, the substance displacement apparatus 200 may alsoinclude a chamber either side of the deflector arm 204, each chamber tohold gas prior to ejection by the gas ejection chamber 202. In theexample shown in FIG. 3, the substance displacement apparatus 200includes a first chamber 306 and a second chamber 308. The chambers 306,308 may be of any shape. In the example shown in FIG. 3, the chambers306, 308 are defined by internal side walls 302 a, 304 a of the firstand second housing portions 302, 304 respectively, the deflector arm 204and front and back walls (not shown) of the first and second housingportions. In some examples, gas may be received in the first and secondchambers 306, 308 through respective gas inlets 310, 312. In thisexample, the gas inlets 310, 312 are in communication with the first andsecond chambers 306, 308 respectively via conduits 314, 316. Theconduits may be formed through the first and second housing portions302, 304. Gas may travel from the chambers 306, 308, through the gasejection aperture 202, towards the roller 102. However, as is clear fromthe discussion below, in some examples, the deflector arm 204 mayrestrict or prevent the flow of gas from one of the first and secondchambers 306, 308, depending on its position.

The substance displacement apparatus 200 may, in some examples, alsocomprise a gas guide element 318 and/or a substance guide element 320.Details and functionality of the gas guide element 318 and the substanceguide element 320 are discussed below.

FIG. 4 is a simplified schematic of an example of the substancedisplacement apparatus 200. In the example shown in FIG. 4, thesubstance displacement apparatus 200 includes the gas ejection aperture202 and the deflector arm 204. The apparatus 200 may further comprisethe gas guide element 318. The gas guide element 318 may be positionedrelative to the gas ejection aperture 202 to guide gas which is directedaway from the target area away from the roller. In some examples, theapparatus 200 may further comprise the substance guide element 320. Thesubstance guide element 320 may be positioned relative to the gasejection aperture 202 to guide gas which is directed towards the targetarea, and the substance removed from the target area, away from theroller. In some examples, the substance displacement apparatus 200 mayfurther comprise the first chamber 306 and the second chamber 308. Thechambers 306, 308 may be either side of the deflector arm 204, eachchamber to hold gas prior to ejection via the gas ejection aperture 202.

FIGS. 5 and 6 are simplified schematics of a portion of the substancedisplacement apparatus 200 shown in FIG. 3, with the deflector arm 204in the first position and the second position respectively. In FIG. 5,the deflector arm 204 is shown in the first position which, in thisexample, is to the left-hand side of the gas ejection aperture 202. Inother examples, the positions may be reversed, such that, in the firstposition, the deflector arm 204 is to the right-hand side of the gasejection aperture 202. Thus, the deflector arm 204 may touch the firsthousing member 302 at the location of the gas ejection aperture 202, andmay be spaced apart from the second housing member 304. In this way,while the deflector arm 204 is in the first position, gas from the firstchamber 306 may be prevented from exiting the first chamber through thegas ejection aperture 202, while gas from the second chamber 308 may beable to exit

-   -   the second chamber through the gas ejection aperture, as        indicated by arrow A.

In FIG. 5, the roller 102 is shown located below the substancedisplacement apparatus 200. However, in other examples, the roller 102and the apparatus 200 may be arranged in any orientation about oneanother. For example, the apparatus 200 may be positioned below theroller 102, as shown in the example arrangement of FIG. 1. It will beapparent that, since the roller 102 rotates with respect to theapparatus 200 in use, the target area on the roller surface will alsomove relative to the apparatus. Therefore, in order to displace asubstance from the surface of the roller 102 within a target area 504,gas may be ejected through the gas ejection aperture 202 towards theroller for a duration that it takes for the whole target area to passunder the part of the gas ejection aperture through which gas isejected.

The gas ejection aperture 202 may be positioned such that gas flowingfrom the first and/or second chambers 306, 308 is directed at leastinitially to towards the roller 102. In the example of FIG. 5, gas thatis able to flow from the second chamber 308 through the gap formedbetween the deflector arm 204 and the second housing member 304 isdirected onto the gas guide element 318. In some examples, the gas guideelement 318 may comprise a lip 502 to prevent gas which is directed awayfrom the target area from flowing towards the target area afterejection. In other words, the lip 502 may prevent the flow of gas (or atleast most of the gas flow) ejected from the second chamber 308 fromreaching the target area. The lip 502 deflects any gas ejected from thesecond chamber 308 away from the target area, generally in the directionindicated by arrow B. In some examples, the gas guide element 318 guidesthe flow of gas along an outer surface of the second housing member 304.The gas may, in some examples, then be recycled, or ejected into theatmosphere.

In other examples, the gas guide element 318 may not include a lip, butthe gas may be directed away from the target area 504 in some other way.In some examples, a shape or configuration of the substance displacementapparatus 200 may cause gas to be directed away from the target area504. For example, the gap formed between the deflector arm 204 and thesecond housing member 304 may be defined by portions of the apparatus200 that are shaped and/or angled such that the gas is directed awayfrom the target area. In some examples, a suction mechanism, or vacuumforming mechanism may be used to suck ejected gas away from theapparatus, and/or the roller 102. Such a suction mechanism may form partof the apparatus 200, or may be associated therewith.

In FIG. 6, the deflector arm 204 is shown in the second position which,in this example, is to the right-hand side of the gas ejection aperture202. In this position, the deflector arm 204 is touching the secondhousing member 304 at the location of the gas ejection aperture 202, andis spaced apart from the first housing member 302. In this way, whilethe deflector arm 204 is in the second position, gas from the secondchamber 308 is prevented from exiting the second chamber through the gasejection aperture 202, while gas from the first chamber 306 is able toexit the first chamber through the gas ejection aperture, as indicatedby arrow C.

In this example, gas flowing through the gap formed between thedeflector arm 204 and the first housing member 302 is directed onto thesurface of the roller 102. Thus, when the deflector arm 204 is in thesecond position, gas may be ejected from the first chamber 306, towardsthe target area 504 of the roller 102, so as to displace a substancefrom the target area of the roller. Gas ejected from the apparatus 200may flow at a rate depending on the intended use (e.g. the nature andamount of substance intended to be displaced). In some examples, therate of flow of gas from the apparatus 200 may depend on the pressure ofgas in the first and second chambers 306, 308. The rate of flow of gasfrom the apparatus 200 may be variable. In some examples, the rate offlow of gas from the apparatus 200 may be sufficient to displace thesubstance from the roller 102.

As noted above, gas ejected from the apparatus 200 while the deflectorarm 204 is in the second position (as shown in FIG. 6) is directed atleast initially towards the target area 504 of roller 102. The ejectedthe gas and/or substance which has been displaced from the surface ofthe roller 102 (and from any cells present in the surface of the roller)may be directed away from the roller by the substance guide element 320.The substance guide element 320 may, in some examples, direct substanceand/or gas away from the roller 102 along a path formed between thesubstance guide element and an outer surface of the first housing member302, generally in the direction indicated by arrow D. In the exampleshown in FIG. 6, the lip 502 of the gas guide element 318 may preventthe flow of gas and/or substance ejected from the first chamber 306 fromflowing into the channel formed by the gas guide element 318 and thesecond housing member 304. In this way, the lip 502 may serve as abarrier to help to deflect substance and/or gas in the direction of thearrow D. Again, in some examples, a suction mechanism, or vacuum formingmechanism may be used to suck ejected gas away from the apparatus,and/or the roller 102. Such a suction mechanism may form part of theapparatus 200, or may be associated therewith.

In some examples, a thickness t of the deflector arm 204 may befractionally smaller than a width of the gas ejection aperture 202. Inthis way, wherein the deflector arm 204 is in contact with one of thefirst or second housing members 302, 304, the gap formed between thedeflector arm and the opposing housing member is relatively small, butlarge enough to allow the gas to flow therethrough. In some examples,the deflector arm 204 may extend at least partially through the gasejection aperture 202. A gap through which the gas is directed may, insome examples, have a width of less than approximately 100 micrometres.In some examples, the gap may have a width of between approximately 50micrometres and 100 micrometres. In other examples, the gap throughwhich the gas is directed may have a larger width. However, a smallerwidth may cause the gas to be ejected at a greater rate, therebyimproving the substance displacement.

In use, the deflector arm 204 may be moved between the first position(shown in FIG. 5) and the second position (shown in FIG. 6) to cause gasto flow onto the surface of the roller 102 in the target area 504, asintended. For example, when it is intended that any substance on thesurface of the roller 102 is to remain (i.e. not be displaced), andtherefore be transferred onto the printable substrate 108, then thedeflector arm 204 may be moved into the first position. In this way, gasfrom the second chamber 308 may be caused to exit the second chamberthrough the gap formed between the deflector arm 204 and the secondhousing member 304, and deflected away from the roller 102, without anysubstance being displaced from the roller surface. If it is intendedthat a particular portion of the printable substrate 108 is to remainunprinted or uncoated, then the deflector arm 204 may be moved into thesecond position. In this position, gas from the first chamber 306 iscaused to exit the first chamber through the gap formed between thedeflector arm 204 and the first housing member 302, towards the targetarea 504 of the roller 102. As the roller 102 rotates, the gas isdirected towards the roller surface, thereby causing any substance onthe surface to be displaced in the direction of the arrow D. In thisway, when the target area 504 of the roller 102 comes into contact withthe printable substrate 108, no substance will be transferred onto theprintable substrate from the target area. Once the roller 102 hasrotated through the extent of the target area 504, the deflector arm 204may be moved into the first position, so as to prevent any furthersubstance from being displaced from the roller surface.

The deflector arm 204 may be moved between the first position in thesecond position in a number of ways. In some examples, the deflector armmay be formed from a piezoelectric material. A piezoelectric material isa material that exhibits the piezoelectric effect (or the reversepiezoelectric effect), whereby a mechanical strain is generated in thematerial in response to the application of an electric field (e.g. avoltage) through the material. Thus, in some examples, the deflector arm204 may be formed from such a piezoelectric material, such that, when noelectric field is applied through the deflector arm, the deflector armis in the first position and, when an electric field is applied throughthe deflector arm, a mechanical strain is generated, causing thedeflector arm to move into the second position. When the electric fieldis removed, the deflector arm 204 may be caused to move back into thefirst position.

In some examples, the deflector arm 204 may be substantially planar inshape. In other words, the deflector arm may have a sheet-likeconfiguration. The width of the deflector arm may, in some examples,depend on the intended resolution at which the substance displacementapparatus 200 is to displace substance from the roller 102. For example,the smallest area on the surface of a roller that could be displaced bya deflector arm 204 having a width of 1 cm would have a width of 1 cm(and a length determined by the duration that the deflector arm remainsin the second position). However, by forming the deflector arm 204 suchthat it has a smaller width, an area on the surface of the roller fromwhich substances to be displaced may be smaller. In some examples, theintended resolution may be less than approximately 2 mm. For example,the resolution may, in some examples, be approximately 1 mm or 0.5 mm.Thus, in such examples, the width of each deflector arm 204 may be 2 mm,1 mm or 0.5 mm. In other examples, the deflector arm may have a largerwidth.

In some examples, multiple deflector arms 204 may be arranged adjacentto one another (e.g. side-by-side). This may increase the width of thearea on the surface of the roller 102 from which substance may bedisplaced. In some examples, the substance displacement apparatus 200may include multiple deflector arms 204, each having a relatively smallwidth, such that the precise area or areas on the surface of the rollerin which substances to be displaced may be accurately selected and/orcontrolled. An example of the use of multiple deflector arms 204 isshown in the example of FIG. 3. In that example, the deflector arm 204may be considered to be a deflector arm array, formed of multipleindividual deflector arms arranged side by side. Such a deflector armarray is shown more clearly in FIG. 7.

FIG. 7 is an exploded perspective view of an example of the substancedisplacement apparatus 200. In this example, the first housing member302 is shown in its normal position relative to the deflector arm 204,while the second housing member 304 shown in an exploded manner,separated from the deflector arm. According to this example, thedeflector arm 204 may include an electrical contact portion 702 and aplurality of deflector arm elements 204 ₁ to 204 _(N). The electricalcontact portion 702 of the deflector arm 204 may receive an electricalcurrent corresponding to one of the deflector arm elements. In someexamples, the electrical contact portion 702 of the deflector arm 204may receive an electrical current corresponding to multiple deflectorarm elements. In some examples, the electrical contact portion 702 maycomprise multiple electrical contact portions. For example, theelectrical contact portion 702 may comprise an individual electricalcontact portion for each deflector arm element 204 ₁ to 204 _(N). Inthis way, the movement of each deflector arm element between the firstposition in second position may be independently controlled.

The present disclosure also relates to method for displacing asubstance. FIG. 8 is a flowchart of an example of a substancedisplacement method 800. The method 800 comprises, at block 802,directing gas from a gas outlet 202 towards a surface of a roller 102,the surface having a substance disposed thereon. At block 804, themethod 800 comprises selectively moving a deflector arm 204 between afirst deflection configuration in which gas is directed away from adefined region on the surface of the roller, and a second deflectionconfiguration in which gas is directed towards the defined region on thesurface of the roller, thereby to displace some or all of the substancefrom the surface of the roller within the defined region. The method 800may, in some examples, be performed by, or using, the substancedisplacement apparatus 200 discussed above.

By displacing a substance from the surface of a roller using the methodsdisclosed herein, the positioning of the substance on a printablesubstrate can be accurately controlled and selected. The disclosedmethods provide a digital alternative to previous methods, in which aplate mounted on the surface of the roller would be replaced when theremoval of substance from a particular area was intended.

FIG. 9 is a flowchart of a further example of a substance displacementmethod 900. The method 900 may comprise, at block 902, directing gasinto a first chamber 306 located at a first side of the deflector armand a second chamber 308 located at a second side of the deflector arm204, the first and second chambers to store the gas prior to beingdirected from the gas outlet 202.

In some examples, gas is directed into the first and second chambers306, 308 so as to maintain a gas pressure in the first chamber 306 whichis approximately equal to a gas pressure in the second chamber 308. Insome examples, the approximately equal pressures in the first and secondchambers 306, 308 may be achieved by maintaining a flow of gas into thefirst chamber when the deflector arm 204 is in such a position orconfiguration that gas is able to exit the first chamber via the gasoutlet 202, and by maintaining a flow of gas into the second chamberwhen the deflector arm is in such a position or configuration that gasis able to exit the second chamber via the gas outlet. In other words,while the substance displacement apparatus 200 is in use, a constantflow of gas may be provided to the first chamber 306 and/or the secondchamber 308. By maintaining an approximately equal, stable pressure inthe first and second chambers 306, 308, the deflector arm 204 is notcaused to move (e.g. between the first and second deflectionconfigurations) as a result of a difference in pressure. Furthermore,with approximately equal gas pressure in both the first and secondchambers 306, 308, the deflector arm 204 may be moved between the firstand second deflection configurations with the application of arelatively low force. Thus, when the deflector arm 204 is formed from apiezoelectric material, movement between the first and second deflectionconfigurations may be achieved using a relatively small power.

In some examples, the pressure of gas in the first chamber 306 and/orsecond chamber 308 may be approximately 5 bar. In some examples, thepressure in the chambers may be higher or lower than approximately 5bar.

As noted above, the deflector arm 204 may, in some examples, comprise apiezoelectric material. In such examples, the method 800, 900, mayfurther comprise applying a voltage to the piezoelectric material tocause the deflector arm 204 to move between the first deflectionconfiguration and the second deflection configuration.

The present disclosure also relates to a print apparatus. The printapparatus may, for example, comprise the substance displacementapparatus 200 disclosed herein. FIG. 10 is a simplified schematic of anexample of a print apparatus 1000. The print apparatus 1000 comprises aroller 1002 having a surface on which to receive a substance to betransferred to a printable medium. The print apparatus 1000 alsocomprises a gas delivery unit 1004 for directing gas towards the roller.The gas delivery unit 1004 may comprise a gas outlet 1006; and a gasdeflector 1008 moveable between a first position in which gas isdirected from the gas outlet away from a target area on the rollersurface, and a second position in which gas is directed from the gasoutlet towards the target area on the roller surface, thereby todisplace at least some of the substance from the target area of theroller surface. The gas delivery unit 1004 may, in some examples,comprise, or be similar to, the substance displacement apparatus 200.

The print apparatus 1000 may comprise any type of print apparatus whichincludes a roller for receiving a substance, such as print agent,primer, ink, varnish, or the like. In some examples, the roller maycomprise an anilox roller, for use in a flexographic print apparatus.

As noted above, the substance displacement apparatus 200, for the gasdelivery unit 1004, may, in some examples, be combined with othersimilar units. FIG. 11 is a simplified schematic of a further example ofa print apparatus 1100 which includes multiple gas delivery units. Theprint apparatus 1100 includes the roller 1002, and may further comprisea plurality of gas delivery units 1004 a to 1004 f, each having a gasoutlet and a gas deflector, the plurality of gas delivery units arrangedlinearly over a length of the roller. In the example shown in FIG. 11,the print apparatus 1100 includes six gas delivery units 1004 a to 1004f. However, in other examples, the print apparatus 1100 may include moreor fewer gas delivery units. As will be apparent from the discussionabove, each gas delivery unit may include multiple gas deflectors. Forexample, each gas delivery unit may include 70 gas deflectors, each gasdeflector having a width of 1 mm. A print apparatus may, in someexamples, include 10 gas delivery units. Therefore, such a printapparatus may include 700 gas deflectors with a resolution of 1 mm. Eachgas deflector may be individually controllable such that the precisearea of the roller from which a substance is to be displaced can beaccurately controlled. Thus, in some examples, the gas deflector 204 ofeach gas delivery unit 1004 may be movable independently of the gasdeflector of each other gas delivery unit.

The present disclosure is described with reference to flow charts and/orblock diagrams of the method, devices and systems according to examplesof the present disclosure. Although the flow diagrams described aboveshow a specific order of execution, the order of execution may differfrom that which is depicted. Blocks described in relation to one flowchart may be combined with those of another flow chart.

While the method, apparatus and related aspects have been described withreference to certain examples, various modifications, changes,omissions, and substitutions can be made without departing from thespirit of the present disclosure. It is intended, therefore, that themethod, apparatus and related aspects be limited only by the scope ofthe following claims and their equivalents. It should be noted that theabove-mentioned examples illustrate rather than limit what is describedherein, and that those skilled in the art will be able to design manyalternative implementations without departing from the scope of theappended claims. Features described in relation to one example may becombined with features of another example.

The word “comprising” does not exclude the presence of elements otherthan those listed in a claim, “a” or “an” does not exclude a plurality,and a single processor or other unit may fulfil the functions of severalunits recited in the claims.

The features of any dependent claim may be combined with the features ofany of the independent claims or other dependent claims.

1. An apparatus comprising: a first chamber formed by a deflector arm and a first housing portion; a second chamber formed by the deflector arm and a second housing portion; the deflector arm positioned within a gas ejection aperture formed by the first housing portion and the second housing portion, wherein the deflector arm is moveable between a first position to allow gas to pass through the gas ejection aperture from the first chamber and a second position to allow gas to pass through the gas ejection aperture from the second chamber; and a roller to receive gas from the gas ejection aperture.
 2. The apparatus of claim 1, wherein the deflector arm is substantially planar in shape.
 3. The apparatus of claim 1, wherein the deflector arm is formed from a piezoelectric material.
 4. The apparatus of claim 1, comprising a gas guide element positioned between a portion of the gas ejection aperture and the roller.
 5. The apparatus of claim 4, wherein the gas guide element comprises a lip to prevent gas from a target area of the roller from flowing towards the target area after ejection from the gas ejection aperture.
 6. The apparatus of claim 4, wherein gas directed through the first portion of the gas ejection aperture bypasses the gas guide element to reach a target area of the roller.
 7. The apparatus of claim 1, further comprising a substance guide element to direct gas displaced from a surface of the roller away from a target area.
 8. The apparatus of claim 7, wherein the target area is a position between the substance guide and a gas guide element.
 9. A substance displacement method comprising: moving a deflector arm from a first housing portion to a second housing portion that forms a gas ejection aperture, wherein the deflector arm makes contact with a surface of the second housing portion that forms a second portion of the gas ejection aperture; directing gas through the gas ejection aperture between the deflector arm and the first housing portion; moving the deflector arm from the second housing portion to the first housing portion, wherein the deflector arm makes contact with a surface of the first housing portion that forms a first portion of the gas ejection aperture; and directing gas through the gas ejection aperture between the deflector arm and the second housing portion.
 10. The method of claim 9, further comprising: directing gas into a first chamber located at a first side of the deflector arm and a second chamber located at a second side of the deflector arm, wherein the first chamber and the second chamber store the gas prior to being directed through the gas ejection aperture.
 11. The method of claim 10, wherein gas is directed into the first chamber and the second chamber so to maintain a gas pressure in the first chamber which is approximately equal to a gas pressure in the second chamber.
 12. The method of claim 9, wherein the deflector arm comprises a piezoelectric material, and wherein the method further comprises: applying a voltage to the piezoelectric material to cause the deflector arm to move between the first housing portion and the second housing portion.
 13. A print apparatus comprising: a roller having a surface on which to receive a substance to be transferred to a printable medium; a gas delivery unit for directing gas towards the roller, the gas delivery unit comprising: a first chamber formed by a deflector arm and a first housing portion; a second chamber formed by the deflector arm and a second housing portion; and the deflector arm positioned within a gas ejection aperture to interact with the second housing portion to open a first portion of the gas ejection aperture and interact with the first housing portion to open a second portion of the gas ejection aperture; and a gas guide element positioned between the gas delivery unit and the roller to receive gas directed through the second portion of the gas ejection aperture.
 14. The print apparatus of claim 13, wherein gas directed through the first portion of the gas ejection aperture is directed on to a target area of the roller.
 15. The print apparatus of claim 14, wherein the gas guide element directs gas received through the second portion of the gas ejection aperture away from the target area of the roller. 